Luminescent cellulose synthetic fiber and method for the production thereof

ABSTRACT

The invention relates to a high-strength luminescent cellulose synthetic fiber, which is produced by means of spin dyeing with a luminescent pigment and a dulling pigment.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a 35 U.S.C. §371 national phase entry application of, and claims priority to, International Patent Application No. PCTEP2012002232, filed May 24, 2012, which claims priority to German Patent Application No. DE 102011102428.3, filed May 24, 2011, the disclosures of which are hereby incorporated by reference in their entirety for all purposes.

BACKGROUND

The invention relates to a luminescent regenerated cellulose fiber containing at least one pigment incorporated during spinning, a process for its production and the use of this luminescent regenerated cellulose fiber.

The requirements for personal protective equipment are increasingly rising and are regulated world-wide by a plurality of standards. The use of personal protective equipment with a warning effect is discussed in detail in EN 471. This standard defines a material as fluorescent if it emits radiation at a wavelength that is longer than the one absorbed. In common parlance, for such materials, the term High Visibility or HiVis has become commonplace.

The currently available HiVis textiles are produced primarily of synthetic fibers, spin-dyed polyester yarns playing a dominant role in the market. As a rule, the extremely low moisture absorption of polyester ( 0.5%) entails low wearing comfort. In order to improve it for HiVis protective equipment, in U.S. Pat. No. 7,312,166, for instance, an elaborate textile structure of a plurality of synergistically acting fibers was developed.

Because with synthetic fibers, there is generally a latent danger of a safety electrostatic charge and, as a result, a high safety risk for the wearer, alternatives to HiVis polyester were sought.

In particular, it is noteworthy to mention HiVis Cotton here, based on the natural fiber cotton, which can be produced by conventional dyeing methods using appropriate fluorescent dyes. This fiber has almost no electrostatic properties and yet is, moreover, distinguished by good wearing comfort. The manufacturing process of HiVis Cotton is, however, not only very cost-intensive but, like every bath dyeing process, has an extremely negative effect on the environment. Moreover, the colorfastness is very hard to achieve and the mechanical load capacity of 100% cotton yarns, and here particularly the abrasion resistance and breaking tenacity is not very high.

When applying the mass dyeing technique to regenerated cellulose fibers, another class of man-made fibers, it has hitherto not been possible to meet the requirements of EN 471. Another technique for regenerated cellulose fibers known from prior art (W02011/032191), the substantially more environmentally friendly spin-dyeing, has hitherto also not achieved the objective. In a recently published review (Lenzing Reports 2006, 85, 87-90), the overall problems of mass spin dyeing of regenerated cellulose fibers is discussed.

An option hitherto available for obtaining a fluorescent regenerated cellulose fiber that complies with standard EN 471 is a two-stage process described in W02011/032191, which is a serial combination of spin dyeing and bath dyeing. In the first process step, a regenerated cellulose fiber is spin-dyed using a color pigment (yellow). In the downstream process step, the fiber is overdyed using a fluorescent colorant, in order to meet the requirements of standard EN 471 by means of it and in particular that of light-fastness in accordance with ISO 105-B02.

Light fastness defines the consistency of paints and varnishes and reflects the fact that sunlight having a high UV content may have a “disintegrating” effect on materials. Standard EN 471 specifies a testing procedure for light fastness of yellow materials using xenon irradiation, wherein “exposure must be carried out until the change corresponds to comparison scale number 4 of the blue scale of level 4 of the gray scale.” Furthermore, the standard specifies that after this irradiation, the minimum luminance factor of the yellow material, for instance, must be greater than 0.7 and that the chromaticity must be within the range specified for the color.

To the man of the art, luminance factor means the ratio of the luminance of a projection screen sample to the luminance of a completely dispersive and reflective surface. Such a surface is also referred to as white reference standard. This procedure is disadvantageous from an economic and an ecological point of view. Two process steps mean significantly higher production costs and bath dyeing is associated per se with a substantially higher negative environmental impact. Moreover, no data in terms of textile mechanics were made regarding the fibers. Rather, the described use in blended yarns suggests that the fluorescent regenerated fibers specified in W02011/032191 are staple fibers. But compared to continuous filaments, with regard to wearing comfort, the hand, and, for instance, the breaking tenacity staple fibers show substantial differences known to the man of the art.

But in view of the applications hitherto of HiVis polyester yarns in protective clothing, e.g. as upper material of warning vests, the mechanical load capacity, expressed as abrasion resistance and breaking tenacity, is extremely significant as far as longevity of the warning item is concerned.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings.

FIG. 1 is a graph illustrating plotted tested fabric data.

FIG. 2 is another graph illustrating plotted tested fabric data.

FIG. 3 is yet another graph illustrating plotted tested fabric data.

DETAILED DESCRIPTION

In contrast thereto, the invention is based on the objective of providing a luminescent regenerated cellulose fiber, which is enhanced as far as its suitability for protection equipment and its manufacturability are concerned. Moreover, the invention is based on the objective of specifying a process for producing this regenerated cellulose fiber, particularly a multifilament yarn and to point out its use.

According to the invention, with respect to the regenerated fiber, this objective is achieved in that the pigment incorporated during spinning is a luminescent pigment and that the fiber additionally contains a dulling pigment incorporated during spinning

Regarding the process for producing a luminescent regenerated cellulose fiber, in which at least one pigment is admixed to the spinning mass and from this mixture, the fiber is spun, the achievement of the objective consists in that the admixed pigment is a luminescent pigment and a dulling pigment is additionally admixed.

Hence, the regenerated fiber according to the invention can be obtained in a single process step of spin-dyeing a suitable viscose using a dispersion of the luminescent pigment and the dulling pigment. The luminescent pigment can be an organic luminescent pigment. The luminescent pigment and the achromatic dulling pigment, which is, for instance, a white pigment, can always be commercially available products. Using the regenerated fiber according to the invention, the standards applicable to protective and warning clothing, in particular the requirements according to EN 471 can be satisfied. A breaking strength of at least 3 cN/tex, preferably at least 10 cN/tex, is achievable. In preferred embodiments, the regenerated fiber according to the invention is a continuous filament with total titers from 67 dtex to 2440 dtex and capillary titers between 0.4 dtex to 22 dtex, particularly between 0.9 dtex to 22 dtex, preferably between 1.8 dtex to 3.3 dtex, and breaking strengths (conditioned, dry) of at least 3 cN/tex, preferably at least 10 cN/tex, more preferred at least 15 cN/tex and particularly preferred at least 25 cN/tex. Furthermore, from the regenerated fibers according to the invention, textile fabrics having abrasion resistances according to Martindale (9 kPa) of at least 20,000 cycles, preferably 45,000 cycles and particularly preferred of 70,000 cycles can be achieved.

The regenerated fiber according to the invention may contain additional additives but the total pigment content of the fiber should be no more than 28%, preferably no more than 25%. In a preferred embodiment, the regenerated fiber is equipped flame-retardant and complies with the standards for protective clothing applicable to it. In particular, the LOI value is at least 24, in particular at least 26. As flame-proofing agents, inorganic and organic pigments can be used, particularly organophosporic compounds having a phosphorus oxidation number of +III to +V, which are added to the spinning mass as a dispersion. Very suitable is a commercially available dispersion of 2,2′-oxybis[5,5′-dimethyl 1,3,2-dioxaphosphorinan] 2,2′disulfide, which is available under the trade name Viscofil® Exolit® 5060 VP2988 from the manufacturer Clariant.

The luminescent pigment is preferably a fluorescent pigment. Phosphorescent pigments differ from it in that, after the effect of irradiation, the latter afterglow in the dark. Particularly in product safety, this property can be used by applying the afterglow after irradiation, e.g. using UV light, as a testing criterion/criterion of authenticity.

In an additional preferred embodiment, the regenerated cellulose fiber is equipped hydrophobizing. Hydrophobization can be achieved by substances known to the man of the art, in particular fluorocarbons, and processes. In this way, not only a water-repellent but also a soil-repellent effect can be achieved. The latter is particularly desirable for applications in the upper material domain.

Within the scope of the invention, in particular the use of the regenerated fiber according to the invention for producing a textile fabric is intended. For this purpose, the regenerated fibers according to the invention can be combined with additional fibers suitable for each of the applications in yarns, from which the textile fabrics are produced, for example by weaving, non-woven methods or knitting. Alternatively, in each case, bare yarns according to the invention and other types of fibers can be jointly processed for producing the textile fabrics. Using these textile fabrics, the requirements of standard EN 471 can be satisfied, so that they are suitable for the manufacture of warning clothing pieces or other warning textiles. Likewise, the standards for the maximum permitted electrostatic charge are met.

All percentual data for proportions of material in the application herein shall mean percent by weight. The invention is explained hereinafter in further detail based on examples:

An aqueous dispersion of a commercially available luminescent pigment and a delustrant, for example titanium dioxide, is stirred in advance in a suitable vessel, in order to achieve uniform distribution of the non-water-soluble pigments. The quality of the pigment dispersion, which is determined by the mean and the maximum particle size, has a significant impact on the fiber properties. Preferably, the maximum particle size, using suitable dispersants, will be below 10 μm, in particular below 5 μm.

Prior to addition to the dissolved cellulose, this dispersion will be subjected to a filtering process, in which particles having a size of more than 25 μm will be retained. The concentration of the cellulose is preferably 5% to 8%, with an a-cellulose content of at least 98%, preferably at least 97.5%.

By means of regulated pumps, a feed stream of the dispersion is added to a feed stream of the cellulose at a fixed ratio. In the total stream, the required homogenization of the dispersion in the viscose matrix is assured by static or dynamic mixers, the period of contact of the pigments with the alkaline viscose to the start of spinning to be adjusted to the chemical resistance of the pigment. During the spinning process, the strength of the yarn can still be influenced, for example by the draw-off speed, elongation as well as the composition and temperature of the spinning bath. Preferably a 2-bath spinning process will be used, the acid concentration in the drawing bath being, in particular, 28% to 30% lower compared to the coagulation bath.

If, as luminescent pigment, the commercially available fluorescent pigment Viscofil Fluorescent Yellow 3G is used, standard EN 471 will only be satisfied if its solids content in the finished fiber is at least around 0.6% and a delustrant is added. Preferably, this solid content is adjusted to values between 0.8% and 12%, in particular between 1.0% and 8%. The solids content of the dulling pigment in the finished fiber is for example between 2% and 24%. The sum of these solids contents in the finished fiber is no more than 28%, preferably no more than 25%.

Surprisingly, it has become obvious that the Viscofil® Exolit® 5060 VP2988 dispersion from the manufacturer Clariant, that is known as a flame-retardant, simultaneously acts as dulling pigment and the latter, therefore, need not be additionally added.

EXAMPLE 1 Exolit 5060 & Viscofil Yellow 3G

With an aqueous dispersion containing 22% Exolit 5060 and 1.9% Viscofil Fluorescent Yellow 3G, using the present process according to the invention, a yarn 200f130 having the following properties is obtained:

Yarn Data:

Breaking Tenancy Breaking Breaking Tenancy Breaking Hot Water Rotation in Conditioned State Elongation in Wet State Elongation Shrinkage Material TPM cN cN100 dtx % cN cN/100 dtx % % 200f130 S250 623 319 7.9 367 188 18.9 14.4

Fabric Data Data of the Tested Fabric

Woven Fabric (WarpWeft 200f130) in Twill Weave

Test Values:

A EN 12127 Mass per unit area g · m² 136.51 A EN ISO 13934-1 Strength - Warp N 944.7 >400 max./min. N 998.0/907.9 Coefficient of Variation %   4.07 95% Scatter Range N □ 33.7   Strength - Weft N 546.8 >400 max./min. N 581.6/495.7 Coefficient of Variation %   5.91 95% Scatter Range N □ 28.3  

x y 0.387 0.61 Measured at D65 D/2 0.356 0.494 Values according to EN 471 0.398 0.452 0.460 0.540 0.387 0.61 β > 0.70 β = Radiance Factor

x y β = Y/100 Specimen 0.4067 0.5055 0.93 unirradiated 0.4077 0.4924 0.8847 irradiated The values are plotted in FIG. 1. This yarn satisfies the standard (see FIG. 1).

Authenticity Test Values A EN ISO 105-C06 Colorfastness in Industrial and Domestic Washing—40° C.

Stage 4/4/4 4/4/4 Process A1S, using steel balls, Evaluation—Gray-scale stage of the color change/immersion in viscose and associated wool fabric

A EN ISO 105-E04 Colorfastness in Perspiration

alkaline Stage 4/3 - 4/3 4/3/3 acidic Stage 4/3 - 4/3 4/3/4 alkaline and acidic solution of a model exudation. Evaluation—gray-scale stage of the color change/immersion in viscose and associated wool fabric

A EN ISO 105-X12 Colorfastness in Abrasion

dry - warp/weft Stage 4-5/4-5 4 wet - warp/weft Stage 4/4 4 Evaluation—gray-scale stage of immersion in an abrasion cotton fabric dry and wet in direction warpweft

A EN ISO 105-D01 Colorfastness in Dry Cleaning Stage 4-53-4 4

Evaluation—gray-scale stage of the color change and immersion in a solvent Solvent used: tetrachlorethylene

EN ISO 105-X11 Colorfastness in Ironing

damp Stage 4 - 5/4 - 5/4 4-5/4/4 wet Stage 4 - 5/4 - 5/4 4-5/4/4 Evaluation—gray-scale stage of the color change of the specimen same/after 4 hours of conditioning in ordinary air for fabric tests/immersion in associated wool fabric temperature 200° C.

Sample 2 (Dulling Agent & Yellow 3G)

With an aqueous dispersion containing 3% TiO₂ and 1.0% Viscofil Fluorescent Yellow 3G, using the process according to the invention, a yarn 167f92 having the following properties is obtained:

Yarn Data

Breaking Tenancy Breaking Breaking Tenancy Breaking Hot Water Rotation in Conditioned State Elongation in Wet State Elongation Shrinkage Material TPM cN cN100 dtx % cN cN/100 dtx % % 167f92 0 592 350 8.7 383 227 21.8 15.5

Fabric Data Data for the Tested Fabric Woven Fabric (WarpWeft 167f92 S90) in Twill Weave

x y 0.387 0.61 Measured at D65 D/2 0.356 0.494 Values according to EN 471 0.398 0.452 0.460 0.540 0.387 0.61 β > 0.70 β = Radiance Factor

x Y β = Y/100 Specimen 0.3935 0.4817 0.8632 unirradiated 0.3892 0.4619 0.8307 irradiated The values are plotted in FIG. 2. This yarn satisfies the standard (see FIG. 2).

Sample 3 (Yellow 3G)

A yarn 167f92 produced using the process according to the invention but not containing any dulling agent but only 1.0% Viscofil Fluorescent Yellow 3G, has the following properties in terms of colorfastness.

Fabric Data: Data of the Test Fabric

Woven fabric (warpweft 167f92 S90) in twill weave

x y 0.387 0.61 Measured at D65 D/2 0.356 0.494 Values according to EN 471 0.398 0.452 0.460 0.540 0.387 0.61 β > 0.70 β = Radiance Factor

x Y β = Y/100 Specimen 0.3973 0.4833 0.8146 unirradiated 0.385 0.4489 0.7887 irradiated The values are plotted in FIG. 3. This yarn does not satisfy the standard (see FIG. 3). 

1. A luminescent regenerated cellulose fiber containing at least one pigment incorporated during spinning, characterized in that the pigment incorporated during spinning is a luminescent pigment, in particular an organic luminescent pigment, and that the fiber contains additionally a dulling pigment incorporated during spinning
 2. The luminescent regenerated cellulose fiber according to claim 1, characterized in that the luminescent pigment is a fluorescent pigment.
 3. The luminescent regenerated cellulose fiber according to claim 1, characterized in that the fiber contains a flame-retardant incorporated during spinning
 4. The luminescent regenerated cellulose fiber according to claim 3, characterized in that the flame-retardant is a dulling pigment.
 5. The luminescent regenerated cellulose fiber according to claim 3, characterized in that its LOI value is at least
 24. 6. The luminescent regenerated cellulose fiber according to claim 3, characterized in that the dulling pigment is an organophosphoric compound, in particular with a phosphorus oxidation number from +III to +V.
 7. The luminescent regenerated cellulose fiber according to claim 1, characterized in that the total pigment content is no more than 28%.
 8. The luminescent regenerated cellulose fiber according to claim 1, characterized in that the fiber is equipped with hydrophobizing.
 9. The luminescent regenerated cellulose fiber according to claim 1, characterized in that its breaking strength at least 3 cN/tex.
 10. A process for producing a luminescent regenerated cellulose fiber, comprising: admixing at least one pigment to a spinning mass, and spinning a fiber from a mixture comprising the admixed pigment and the spinning mass, characterized in that the admixed pigment is a luminescent pigment and wherein the process further includes additionally admixing a dulling pigment.
 11. The process according to claim 10, characterized in that the viscose content of the spinning mass is in the range of 3% to 9%.
 12. The process according to claim 10, characterized in that the mean particle size of the pigments is no more than 10 μm.
 13. The process according to claim 10, characterized in that the α-cellulose content of the spinning mass is at least 90%.
 14. The process according to claim 10, characterized in that the pigment content in the fiber is no more than 28%.
 15. The luminescent regenerated cellulose fiber of claim 1, wherein the regenerated fiber is included in a textile yarn.
 16. The luminescent regenerated cellulose fiber of claim wherein the fiber is included in a textile fabric.
 17. The luminescent regenerated cellulose fiber of claim 16, wherein the textile fabric complies with standard EN
 471. 18. The luminescent regenerated cellulose fiber of claim 16, wherein the textile fabric is characterized in that its abrasion resistance according to Martindale is at least 20,000 cycles (a 9 kPa).
 19. The luminescent regenerated cellulose fiber of claim 16, wherein the textile fabric is used for manufacturing a warning garment or warning textile. 